In a conventional cooling system, for example in a vehicle, the cooling medium pump for cooling the engine is operated in such a way that the flow varies depending on the engine speed. The control valve is used to control the flow of the pump, either to the radiator or back to the pump depending on the temperature of the flow, which leaves the engine. The capacity of the flow in a conventional system is dimensioned to manage engine operation under full load conditions, such as driving in an upward slope with a full throttle. Normally, the bypass line is also dimensioned for approximately the same amount of flow, which flows through the radiator so that the thermostat control can be as efficient as possible.
Accordingly, the flow capacity is not optimized for normal operation conditions, which means that the pump operates with high effect independent of the operation conditions. Consequently, the operation of the cooling medium pump results in considerable power dissipation, which effects the engine efficiency.
It is desirable to reduce this power dissipation without influencing the construction in a negative way, for example, avoiding that it becomes more bulky or considerably expensive to produce.